Nature and(in-)coherent metamorphic evolution of subducted continental crust in the Neoproterozoic accretionary collage of SW Mongolia

In continental subduction complexes minor volumes of high-pressure mafic rocks(eclogites) often co-exist with much more abundant felsic(granitic) and metasedimentary rocks, which are vital for resolving the origin and metamorphic evolution of subducted continental crust.In SW Mongolia, the Alag Khadny eclogite-bearing accretionary complex(AKC) is assumed to represent either a remnant of oceanic slab, or a continental margin,subducted in the Early Cambrian.Here we present geochronological, geochemical and petrological evidence of subduction records for the three major types of lithologies that host mafic eclogites, including Mesoproterozoic and Neoproterozoic granitic basement and overlying Neoproterozoic continental-margin sediments.Variably deformed, ferroan and peraluminous metagranitoids compose a major part of AKC and are interlayered with eclogites in its southern and eastern margins.They have geochemical features of post-collisional/intraplate high-K calc-alkaline granites.LA-ICP-MS U-Pb zircon geochronology of three distinct metagranite samples show uniform protolith crystallization ages of ca.0.96 Ga and uncertain re-crystallization in the Late Neoproterozoic or Early Paleozoic metamorphic event, whereas abundant zircon inheritance indicates older,Mesoproterozoic to Paleoproterozoic crustal substrate during granite generation.The existence of Mesoproterozoic crust is highlighted by finding of distinct metagranitoids with the U-Pb zircon crystallization age of ca.1.6 Ga.Hafnium isotope signatures(T_(DM)~C 2.88–1.85 Ga) of zircons from all lithologies preserved the evidence of reworked Neoarchean to Paleoproterozoic crust, similar to that of the Baidrag block(southern Mongolia), for both Mesoproterozoic and Neoproterozoic rocks.Regardless of the specific lithology, the rocks display indicators of high-pressure metamorphic re-equilibration, including garnet(X_(Ca)up to 0.65) + epidote +phengite(Si p.f.u.up to 3.56) ± rutile assemblage in metagranitoids, garnet + phengite(Si p.f.u.up to 3.42)in quartz-rich semi-pelites and garnet + phengite(Si p.f.u.up to 3.39) + medium-Mg chloritoid(X_(Mg)up to 0.25) + kyanite + rutile in metapelites.Corresponding P-T conditions recovered from different lithologies reveal incoherent subduction of rocks, which could be shallow for granitic basement(1.1–1.4 GPa and 600–670 ℃) and clastic metasediments(1.4–1.6 GPa, 570–620 ℃), but deeper for metapelites(2.1–2.3 GPa, 500–570 ℃).consistent with that of eclogites, The combined data show that the Alag Khadny complex represents a remnant of a rifted Mesoproterozoic to Neoproterozoic(ca.1.6–0.96 Ga) continental margin consequently metamorphosed under HP conditions during Late Neoproterozoic–Early Cambrian evolution of the southern Central Asian Orogenic Belt.Acquired P-T estimates imply that high-pressure metagranitoids and metasedimentary rocks equilibrated at different depths, but most likely shared a common subduction-related metamorphic evolution.     

Sicilian serpentinite xenolihs conaining abioic organics wih nanodiamond clusers ans key model for prebioic processes

Rock fragments from the deepest parts of a buried hydrothermal system belonging to the Mesozoic Tethys Oceanentered as xenoliths in a Miocenic diatreme. hence b...     

Dust torus formed by particles ejected from a celestial body at an arbitrary point of its elliptic orbit

Dust comnplexes make one of the components of the Solar System. The surface shape of a typical dust complex consisting of particles ejected by a celestial body is found analytically, under reasonable assumptions (the main one being the smallness of perturbations). Parametric equations of the surface are obtained. The main properties of the surface are established and studied. Singular points are found, and the topological type of the surface as a whole and in the vicinity of the singular points (one conic points and one constriction) is examined.     

New Experimental Platform for Studies of Turbulence and Turbulent Mixing in Accelerating and Rotating Fluids at High Reynolds Numbers

We present a new experimental platform for studies of turbulence and turbulent mixing in accelerating and rotating fluids. The technology is based on the ultra-high performance optical holographic digital data storage. The state-of-the-art electro-mechanical, electronic, and laser components allow for realization of turbulent flows with high Reynolds number (>10⁷) in a relatively small form-factor, and quantification of their properties with extremely high spatio-temporal resolutions and high data acquisition rates. The technology can be applied for investigation of a large variety of hydrodynamic problems including the fundamental properties of non-Kolmogorov turbulence and turbulent mixing in accelerating, rotating and multiphase flows, magneto-hydrodynamics, and laboratory astrophysics. Unique experimental and metrological capabilities enable the studies of spatial and temporal properties of the transports of momentum, angular momentum, and energy and the identification of scalings, invariants, and statistical properties of these complex turbulent flows.     

The problem of clock synchronization: A relativistic approach

The problem of synchronization of the Earth-based clocks has been discussed in the framework of General Relativity Theory. The synchronization is considered as the transformation of the observers' proper time scales to the coordinate time scale of local inertial geocentric reference system, which is single for all the observers. The formulas for the relativistic corrections occurring in some methods of Earth-based clock synchronization (transported clock, duplex communication via geostationary satellite and meteor-burst link, LASSO experiments) have been derived enabling one to attain the accuracy of 0.1 ns.     

A new approximate solution of parallel whistler-mode dispersion equation

A new approximation of the real part of the nonrelativistic plasma dispersion function ?Z of a real argument ξ₀ is proposed: namely, $$\Re Z_A (\xi _0 ) = \frac{{2\xi _0 }}{{1 - 2\xi _0^2 }}.$$ This approximation gives the exact value for ?Z when d²?Z/dξ ₀ ² = 0 and gives the correct expressions for the first two terms of its expansion for large ξ₀. On the basis of this approximation, a new approximate expression for whistler-mode refractive index is derived for the case of wave propagation parallel to the magnetic field in a hot anisotropic and dense plasma. Under certain conditions this expression is more convenient for practical applications in magnetospheric and/or astrophysical conditions than other approximate expressions. The approximation ?Z _A was also used in deriving the approximate expression for whistler-mode instability or damping (γ), although in this case it seems to have little merit when compared with the previously used expressions for γ.